Tagging is a process by which users assign labels in the form of keywords to contents with a purpose to share, discover and recover them. Discovery enables users to find new and interesting objects shared by other users. Recovery enables a user to recall objects that were previously discovered. Recently, an increasing number of tagging services are becoming available on the web, such as the FLICKR(™) Web service, the DEL.ICIO.US(™) Web service, the My Web 2.0 Web service, the RawSugar Web service and the SHADOWS(™) Web service. The FLICKR(™) Web service enables users to tag photos and share them with contacts or make them publicly available. The DEL.ICIO.US(™) Web service allows users to tag uniform resource locators (URLs) and share tagged URLs with the public. The My Web 2.0 web service provides a web-scale social search engine to enable users to find, use, share and expand human knowledge. It allows users to save and tag Web objects, allowing for browsing and searching of objects, as well as sharing Web objects within a personalized community or to the public. Further, the My Web 2.0 Web service provides scoped searches within a user's trusted social network (e.g., friends and friends of friends). As a consequence, the search results are personalized and spam-filtered by trusted networks.
Tagging advocates a grass root approach to form a so-called “folksonomy”which is neither hierarchical nor exclusive. With tagging, a user can enter free form labels to tag any object; it therefore relieves users of much of the burden of fitting objects into a universal ontology. A user may also utilize tag combinations to express interest in contents tagged by other users, e.g., the tags (renewable, energy) for objects tagged by both the keywords renewable and energy.
Those of skill in the art recognize that ontology works well when the corpus is small or in a constrained domain, the objects to be categorized are stable and the users are experts. A universal ontology, however, is difficult and expensive to construct and to maintain when dealing with a large group of users (e.g., hundreds of thousands) with diverse backgrounds. When used to organize Web objects, ontology faces two hard problems: unlike physical objects, digital contents are seldom semantically pure so as to fit in a specific category; and it is difficult to predict the paths through which a user would explore to discover a given object. Taking a directory of Web objects as an example, a recipe book belongs to both the categories shopping and health, since it is hard to predict which category an end user would perceive to be the best fit.
Tagging bridges some gap between browsing and search. Browsing enumerates all objects and finds the desirable one by exerting the recognition aspect of human brain, whereas search exercises the association aspect that dives directly to the interested objects, which is less mentally taxing. The benefits of tagging, however, do not come without a cost. For example, the number of tags tends to multiply at an exorbitant rate. Furthermore, the structure of a traditional hierarchy disappears. Tagging relates to faceted classification, which uses clearly defined, mutually exclusive, and collectively exhaustive aspects to describe objects. For example, a music piece can be identified by facets such as artist, albums, genre, and composer. Faceted systems fail to dictate a linear order in which to experience the facets, a step crucial for guiding users when exploring an information system. Since tags are created by end-users in a free form, the tag collection may lack order and depth when compared to a faceted system constructed by experts. This lack of order and depth can result in a disaster, leaving the users muddled in front of a “hodgepodge.”
Therefore, what is need is a system and method that overcome the above-noted short-comings and provide an efficient and effective means for tagging content for sharing, discovery and recovery.